1. Field of the Invention
The present invention relates to an inkjet printing apparatus that adopted the inkjet system.
2. Description of the Related Art
Conventionally, for the inkjet printing apparatus, a printing apparatus in which ink ejection ports are arranged over the whole length equivalent to a width of a printing medium, namely the printing apparatus of a full line type, is proposed. When manufacturing a long-length ink ejection head that is used in the printing apparatus of a full line type, constructing it by arranging a large number of nozzles on a single board with a high density is accompanied by many difficulties in terms of technology and costs. Therefore, it is proposed to realize the long-length ink ejection head by arranging a plurality of short-length ink ejection units (hereinafter referred to as a “chips”) that are relatively cheap and easy to manufacture. There is proposed a head in which the chips each having a plurality of ink ejection ports (hereinafter, also referred to as “nozzles”) are placed staggeredly so as to overlap each other in a direction perpendicular to the nozzle row 11.
Below, the head in which the short-length chips are arranged so as to overlap each other is called a “overlapping head”, an overlap area is called a “overlapping portion”, and an area where the chips do not overlap is called a “non-overlapping portion”. Since the overlapping portion forms an image with a plurality of chips, the image is formed with a large number of ejection port rows compared with the non-overlapping portion. Therefore, a method of selectively using the ejection ports in the overlapping portion has been disclosed.
Japanese Patent Laid-Open No. 2005-161733 discloses a method: first it is judged whether an end part of an image to be printed is included in the overlapping portion of the chips that overlap each other; and if it is included, overlapped nozzles corresponding to the overlapping portion of the chips and nozzles other than the overlapped nozzles that communicate that overlapped nozzles are used as a group of nozzles to be used.
Incidentally, a case where the printing is performed by the overlapping portion brings a following merit. Generally, when the image is formed using a plurality of chips of the overlapping portion, it exerts an effect of reliving deviations of an ejection direction and the amount of ejection that each nozzle has, so-called an effect of multi-pass printing, and the image is improved. In addition, conversely, the overlapping portion also comes with a disadvantageous point: an image may deteriorate because of impact displacement between the both chips forming the overlapping portion.
Generation of such impact displacement will result in occurrence of image deterioration, such as a texture, a moire, and a streak. In terms of this point, it can be said that printing with a single chip is advantageous. That is, in the overlapping portion, a merit that the both chips overlapping each other are used exists and a merit that a single chip is used exists, respectively, and they are in a tradeoff relationship. A factor is the dot impact accuracy between the chips, and the dot impact accuracy of a chip alone.
The above-mentioned conventional technology discloses that the overlapping portion is formed with a single chip. This is only paying attention to one of the problems: it does not refer to the problems that become a tradeoff as described above and does not solve it.